Due to the tradition of not using girls in church choirs, boy sopranos are often still simply called "trebles" even when the gender of the singers is not mentioned, but girls with high voices are trebles too. Even the Concise Oxford Dictionary of Music makes this mistake on p. 689 (A boy soprano is known as a treble.) though it points out on p. 746 that all children with high voices are known as trebles.
